. XII. XIII. EFFECTS ON THE MUSCLES. 233 



muscle at the closure of the circuit, are more persistent 

 than those which take place at the opening of it. The 

 latter re-appear when the intensity of the current is aug-' 

 mented. 



We may, therefore, conclude, that when the electric 

 current acts on a muscular mass deprived of its visible 

 nervous filaments, it excites contractions therein, both when; 

 the circuit is closed and when it is interrupted, whatever' 

 may be the direction of the current relatively to that of the 

 muscular fibres ; and, also, that the contractions which take 

 place when the circuit is opened are the first to disappear. 



If the discharge be that of a Leyden bottle, which is made 

 to pass across a muscle, for example, the gastrocnemius 

 of a frog, it is curious to observe that the muscle contracts 

 and continues in this state. 



It now remains for me to notice the various circumstances 

 which modify the action of the current on the nerves and 

 muscles of living, or recently killed animals. 



The voltaic alternatives, of which I am now about to speak, 

 are the result of the same passage of the current in the 

 nerve. Observe in what this phenomena consists. We 

 put a frog, prepared in the usual way, across two small 

 glasses, containing pure, or slightly saline water, in such a 

 way that the spinal marrow is immersed in one glass, and 

 the legs in the other. We then close the circuit. If we 

 allow the current to circulate for a certain time, say twenty 

 or thirty minutes, according to the strength of the current, 

 and then open it and close it again, no further contractions 

 are obtained. But by reversing the direction of the current, 

 the contractions re-appear; and they cease again, more 

 speedily than in the preceding one, when the passage of 

 the current has been prolonged. By again reversing the 

 direction of the current, that is, by re-establishing it as it 

 was at the commencement of the experiment, the contrac- 



